Multi-sectional roof cap for mine roof supporting prop means



G. DOMMANN ET Al. 3,455,113

July 15, 1969 MULTI-SECTIONAL ROOF CAP FOR MINE ROOF SUPPORTING PROP MEANS Filed July 17, 1967 S P mm NmnV/w EH0. b... V N N n m W 4 W W V. m m J G Int. Cl. E2111 17/00; F16c 11/04 US. CI. 61-45 7 Claims ABSTRACT OF THE DISCLOSURE Multi-sectional roof cap for mine roof supporting prop means or chock, e.g., used in longwall mining, including a pair of longitudinally extending individual roof cap sections interconnected articulately at their adjacent ends by a common transverse pin, supportable on such prop means, and a leaf spring supported medially against displacement on such pin as a fulcrum with the spring free ends maintained in urging surface contact upwardly against the adjacent roof cap section ends joined by the pin, whereby to prevent tilting of the cap sections and concomitant raising of the pin joint into dragging contact with the mine roof.

The present invention relates to a multi-sectional roof cap for mine roof supporting prop means and more particularly to such a cap composed of at least a pair of individual cap sections articulately interconnected by a common transverse pin and containing leaf spring means supported medially against displacement on the pin and having corresponding free ends in urging surface contact with the underside portions of the roof cap section ends joined by the pin.

Multi-sectional roof bars or roof caps for mine roof supporting prop means such as prop chocks are known. These are used to support the mine roof in connection with longwall mining operations. Usually, the multi-sectional cap includes at least two individual cap sections articulately interconnected by a common transverse pin with each cap section being mounted on at least one mining prop or pit prop, i.e., extensible and retractable hydraulic jack, so as to permit the chock to support the roof while also permitting longitudinal displacement of the chock, and in turn of the cap sections, toward newly exposed layers of the mine face as the work progresses. Where such longitudinal advance of the chock toward the mine face is desired, the prop means are relaxed slightly to minimize friction and drag between the roof caps and the roof, but in doing so, the individual sections often deviate from the normal horizontal position due to the cantilever nature of their mounting on the appropriate mining props.

To minimize such deviation or slanting of the individual sections of the cap, leaf springs have been provided at the transverse pin joint between the articulately connected sections, such leaf springs being connected both in the area of the upper cord and in the area of the lower cord of the individual sections. Specifically, the extremities of the leaf springs were connected to the roof cap sections by means of a pin passing transversely through each roof cap section. In order to accommodate the seating pins for the extremities of the leaf springs, expensive machining operations have to be performed on the roof bars or caps, i.e., individual sections, similar to the operations necessary for installing the appropriate bearings for the transverse pins. The consequence of providing such leaf springs is to prevent as far as possible States atent O f 3,455,ll3 Patented July 15, 1969 the cantilever slanting of the individual sections with respect to one another at the pin joint in question, yet because of the expensive machining operations necessary and the inherent weakening of the roof cap in the immediate area of the holes necessarily made to accommodate the leaf spring pins, much in the way of advantages in preventing the slanting of the caps is lost in the inherent weaknesses which result in the modified cap construction. Specifically, in order to offset the weakening of the roof caps by reason of the holes made therein, the caps are constructed of a greater web width than usual, and this oversizing of the cap and the additional expenses involved in providing the leaf spring pins influence adversely both the weight and cost factor. Accordingly, spring elements spanning the joint between articulately interconnected roof cap sections have not been used, as a rule, to avoid the disadvantageous slanting of the sections when the cap is lowered from the roof in order to be advanced.

The problem of roof bar slanting is particularly acute in the case of the commonly cantilevered roof bars of prop chocks associated with longwall mining techniques. Specifically, the forwardmost cap is cantilevered on the appropriate mining prop such that twoathirds of its length extends beyond the particular prop in the direction of the mine face to protect preliminarily as much of the mine roof overlapping the planer alley as possible. On the other hand, the distance between the prop and the rear joint amounts to only about one-third of the total cap length, so that the greater lever arm inherently exerts a tendency on the forward end of the cap to tilt downwardly when released from the roof, with concomitant upward lifting of the rear end, and in turn the pin joint connection with the next adjacent cap of the chock therebehind. The upward swing of the pin joint connection against the roof during the release of the cap in order to move the chock forwardly toward the mine face is particularly disadvantageous when the release is only sufliciently slight to enable the chock to be advanced with a minimum removal of roof support thereat. Since the joint between the adjacent roof cap sections necessarily will drag against the roof, the guidance of the chock in the longitudinal direction of advance is rendered considerably more diflicult than is normally the case.

Attempts to overcome the problem of tilting or slanting roof cap sections when such caps are retracted slightly from the roof for advance by filling the shorter end of the particular section with ballast to counterbalance the longer end portion have not been satisfactory because the considerable amount of weight added thereby renders the cap sections more difficult to install and remove from atop the mining props.

It is an object of the present invention to overcome the foregoing drawbacks and to provide a modification of existing equipment by the use of a novel arrangement of leaf spring reinforcement of the articulation joint between appropriate ends of multi-sectional roof bars or caps to avoid tilting or drag on the roof of such caps, especially when released slightly from the roof in order to be displaced longitudinally.

It is another object of the present invention to provide a multi-sectional roof cap composed of at least two individual roof cap sections interconnected articulatedly by a common transverse pin with a leaf spring supported medially against displacement on the pin as a fulcrum such that the free ends of the spring are mounted in urging surface contact disposition upwardly against the adjacent underside portions of the roof cap section ends joined by the pin.

It is still another object of the present invention to provide a construction of the foregoing type in which the leaf spring reinforcement may be added to existing constructions without being directly fastened to the caps,

without the necessity for modifying the cap construction by expensive machining operations, involving the installation of bearings for leaf spring attachment pins, without weakening the cap construction, without enlarging concomitantly the cap construction or providing a greater web width, and generally without adding to the weight and cost factor of the system.

It is a still further object of the present invention to provide a construction of the foregoing type which avoids drag and friction on the roof during advance of the cap system and which in turn avoids concomitant difficulties in proper guidance of the chock along the normal longitudinal path of advance.

It is a still further object of the present invention to incorporate leaf spring means at the articulation joint between individual sections without increasing the weight or cross section thereof and without weakening the disposition thereof and thus without rendering such caps more difficult to install and remove.

Other and further objects of the present invention will become apparent from a study of the within specification and accompanying drawing, in which:

FIG. 1 is a schematic longitudinal cross-sectional view of one embodiment of a multi-sectional roof bar or cap in accordance with the present invention;

FIG. 2 is a schematic top view of the embodiment shown in FIG. 1;

FIG. 3 is a schematic longitudinal cross-sectional view of a modification of a multi-sectional roof bar similar to that of FIG. 1; and 1 FIG. 4 is a schematic longitudinal cross-sectional view of a further modification of a multi-sectional roof cap similar to those of FIGS. 1 and 3.

It has been found in accordance with the present invention that a multi-sectional roof cap may now be provided which avoids the downward tilting of the individual ends of articulatedly interconnected roof cap individual sections while at the same time preventing upward displacement of the interconnecting joint into contact with the roof where the prop means carrying the roof cap are retracted sufficiently to permit advance of the chock and roof cap sections. Thus in accordance with the present invention, a multi-sectional roof cap for mine roof supporting prop means may be provided which comprises a pair of longitudinally extending individual roof cap sections interconnected articulatedly at their adjacent ends by a common transverse pin and adapted individually to be mounted on and extended by a corresponding prop means into roof supporting engagement, and at least one leaf spring supported medially against displacement on said pin as a fulcrum with the corresponding free ends of said spring maintained in urging surface contact disposition upwardly against the correspondingly adjacent underside portions of said ends of said roof cap sections joined by said pin.

Preferably the spring is bowed medially and extends in form fitting surface contact with the upper side of said pin while the free spring ends are maintained in said urging surface contact disposition against said underside portions.

In accordance with one modification of the present invention, the free spring ends are provided with corresponding threaded apertures and coacting adjustment screws inserted upwardly therethrough having the corresponding screw ends in contact with said underside portions whereby to vary the spring force against said underside portions and in turn vary the vertical disposition of the corresponding ca-p section with respect to said pin.

The pin may also carry a collar thereon in accordance with a further modification such that the collar is provided with a spring seating portion, whereby the spring is supported medially against displacement on the collar while the free spring ends are maintained in urging surface contact disposition against the cap underside portions. The spring may be further provided with a medial threaded aperture and coacting medial adjustment screw inserted upwardly therethrough and seated in a corresponding threaded connection defined in the underside of said collar to connect vertically adjustably said spring to said collar whereby to vary the spring force against said underside portions and in turn vary the vertical disposition of the corresponding cap section with respect to said pin.

The spring may be a single band leaf spring or a compound leaf spring in the form of a spring bundle having at least two leaf spring members therein.

Referring to the drawing, in FIGS. 1 and 2, a multisectional roof cap is shown in part including the individual roof bar or roof cap sections 1 and 2 articulately interconnected at their adjacent ends by means of a joint having the common transverse pin 3 in the well known manner and adapted to be carried at the prop seats P on appropriate mining props of a mining support system such as a prop chock. The pin 3 is carried specifically in the bearings 11 and 12 located on the appropriate ends of the cap sections 1 and 2.

In accordance with the present invention, a leaf spring 6 is supported medially against displacement on pin 3 which acts as a fulcrum such that the free ends 7 and 8 of the spring are maintained in urging surface contact with the bottom cords 4 and 5 at the adjacent underside portions of the cap sections, whereby to urge the cap sections 1 and 2 upwardly and thus prevent rotation of the cap sections downwardly and toward one another about the axis of pin 3. This would normally occur when the mining props on which the sections 1 and 2 are mounted are lowered from roof supporting engagement so as to permit the common joint portion of the multi-sectional roof cap to swing upwardly while the distal ends swing downwardly due to their greater length and weight and the resulting lever effect, considering the space provided between the cap and roof caused by the lowering.

Since the leaf spring 6 contains an arcuate medial portion mounted over the upper half of pin 3 and since the leaf ends are normally biased in upper direction, the ends or extremities 7 and 8 urge the bottom cords 4 and 5 upwardly with respect to the pin axis as fulcrum, yet the construction provided will entail little or no modification of existing equipment to achieve the efficient results described. It should be noted that the relationship of the leaf spring 6 with respect to the common transverse pin 3 and the undersides or cords 4 and 5 is such that no direct attachment between the spring and the roof cap parts is necessary or contemplated.

However, if desired, adjusting screws 9 and 10 may be mounted at the ends 7 and 8 of spring 6 by the simple expedient of providing threaded apertures at such ends to accommodate the screws. Even so, no modification of the cap sections themselves is necessary in accordance with this feature. By adjusting the screws 9 and 10, the extremities 7 and 8, as the case may be, will be maintained in the normal spatial relation whereas the cap ends themselves will be permitted to be displaced downwardly slightly so as to facilitate travel of the arrangement in longitudinal direction, as for example where the chock on which the multisectional roof cap is mounted is to be advanced toward a longwa'll mine face, i.e., so as to avoid drag between the upper surfaces of the cap sections and the roof, especially in cases where the roof is uneven.

In FIG. 3, a modification of the arrangement is shown, including the cap sections 1' and 2', the common pin joint articulation via the transverse pin 3 carried by the appropriate bearings 11 and 12', and the leaf spring 6' having the bowed extremities 7' and 8' in contact with the undersides or bottom cords 4 and 5' of the sections. In this construction, however, gusset plates 13 and 14 are provided on the undersides or cords 4 and 5' as additional support of the joint due to the downwardly directed disposition of the bearings 11 and 12, and in turn of the lower positioning of the pin 3'. In consequence of this modification, the spring 6' need not be as sharply bent as in the case of the medially bowed spring of FIG. 1. In the modification of FIG. 3, as in the case of the arrangement shown in FIG. 1, the spring is mounted on the upper half of the corresponding pin and the spring ends are loaded against the undersides or cords of the corresponding cap section ends without the necessity for any fastening means whatsoever to connect directly or indirectly the spring to the parts controlled thereby.

In the case of the modification of FIG. 4, a similar multi-sectional roof cap joint is shown to that in FIG. 3 wherein the individual sections 1" and 2" are connected articulatedly via a pin 3" in a downwardly displaced position (similar to the bearing construction of FIG. 3), but in this instance the spring 6" is connected to a collar 15 mounted on the transverse pin 3" such that the ends or extremities 7" and 8 of the spring act in the desired upwardly urging direction against the undersides or bottom cords 4" and 5 of the sections. The leaf spring shown in this embodiment is provided in the form of a multiple or compound leaf spring containing the individual leaf springs 6a and 6b connected as a spring bundle by any appropriate means. While the spring 6 may be connected directly to the collar 15, it is desirable to achieve such connection by providing an adjusting screw 16 engaging a threaded opening in the underside of collar 15. Spring 6 is thus vertically adjustable at its center portion with respect to the collar 15 and thus with respect to the pin 3" which still acts as fulcrum.

Of course any other type of intermediate connection similar to collar 15 may be utilized for interconnecting the spring 6" with the pin 3" for the desired purpose with or without an adjusting screw to achieve vertical displacement of the spring with respect to the pin. The purpose of such vertical adjustment is generally to permit relaxation of the upward urging of the corresponding cap section ends by the extremities 7" and 8 of the spring, as for example when it is desired to negotiate uneven areas of the roof along which the multi-sectional roof cap is conducted in slightly lowered position when the chock or other prop means on which the cap means is mounted is to be advanced in a given direction. Thus, the adjustment screw 16 serves a similar purpose to the adjustment screws 9 and 10 in the embodiment shown in FIG. 1.

In the case of all of the embodiments contemplated herein, the desired leaf spring arrangement may be incorporated on existing equipment without the need for modifying such equipment in any way. The leaf spring in the embodiments of FIGS. 1 and 2 on the one hand and FIG. 3 on the other hand is merely disposed with its medial portion in surface supporting contact against the upper side of the appropriate transverse pin such that the spring extremities act upwardly against the undersides of the adjacent ends of the cap sections. In the case of the embodiment of FIG. 4, the spring extremities act in a similar manner, but the fulcrum in this case is attained with a spring, avoiding the use of an arcuate medial portion by providing instead an intermediate connector or collar in surface contact With the upper side of the pin such that the spring may be simply connected to the collar, for example at a point below the pin. While a connection is in fact provided between the spring and collar in the modification embodiment of FIG. 4, there is still no need for direct fastening of the spring and collar assembly to the pin since the collar by its very configuration serves as fastening means without modification of the pin or cap sections to achieve the collar mounting.

Accordingly, the construction of the present invention avoids the need for attaching leaf springs across the articulated joint both in the vicinity of the upper cord or surface and lower cord or surface of the respective cap section, and also the need for pin connections between the spring extremities and the cord surfaces in question. In turn, the previously necessary expensive machining operations performed on the cap sections to install bearings for connecting pins between the spring extremities and the cap ends are no longer necessary nor is there any weakening of the cap sections in the vicinity of any such bearing installations. Furthermore, the cap sections need not be reconstructed with a greater web width nor reinforced in any way beyond the normal requirements. The weight and cost factor involved in providing the modifications of the present invention on existing equipment is therefore minimal and the spring loaded construction obtained in accordance with the present invention enables the cap sections to be maintained in the normal horizontal disposition, with the cap sections being able to be lowered slightly from the roof without tilting of the distal cap ends downwardly and without tilting of the pin joint upwardly, and accordingly without difficulties in guiding the chock during the desired advance as would otherwise be caused by dragging of the pin joint against the roof. Furthermore, the need for ballast to counterbalance the respective lever ends of the cap sections is avoided and the concomitant additional weight forced onto the system by this expedient. Therefore, the caps containing the spring modification of the present invention are no more difficult to install and remove than heretofore. Simple form fitting spring means are employed in accordance with the present invention which are in no way fastened to the existing parts, but merely supported thereon by surface contact directly or indirectly.

It will be understood that the leaf springs may be in the form of a simple or compound leaf spring, i.e., a single element or a bundle of leaf spring elements, with the latter feature being particularly applicable where the connection between the spring and the pin takes place via an intermediate collar, or the like.

Where adjusting means, such as adjusting screws, are provided either at the extremities of the spring or at the medial portion thereof, for example in the case of the modification of FIG. 4, such adjustment means in no way require modification of the original equipment. The adjustment screws contemplated on the spring extremities merely bear against the underside of the cap ends in question so that there is no need for special threading of the caps, yet versatility in operation will be enjoyed since by screw adjustment the adjacent cap ends may be depressed slightly to negotiate irregularities or unevenness in the roof or may be raised to cause corresponding depression of the distal ends of the cap sections for the same purpose. The slight raising and lowering of the adjacent and distal ends of the cap sections in question in order to avoid drag at the roof and concomitant misguidance of the chock during advance may be achieved whether the adjustment means are in the form of adjustment screws or other adjustment means and whether such adjustment means are located at the spring extremities or at the center of the spring.

It will occur to the artisan that similar adjusting means may be provided to effect the same purpose such as a tensioning couple, for example a turnbuckle connection, interconnecting the end portions of the spring and linearly adjustable to force the spring ends inwardly or outwardly with respect to one another.

Naturally, where various constructional parts have been defined in terms of means in the instant specification and/ or claims, such means have been illustrated in the accompanying drawing as specific elements, but in accordance with the present invention, such means contemplate any and all elements usable to achieve the combination arrangement of the invention, as the artisan will appreciate, so long as the disposition of the parts in question is maintained, and any and all such constructional elements are contemplated herein just as if prolix enumeration thereof were set forth in detail herein.

It will be appreciated that the instant specification and drawing are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention which is to be limited only by the scope of the appended claims.

What is claimed is:

1. Multi-sectional roof cap for mine roof supporting prop means which comprises a pair of longitudinally extending individual roof cap sections interconnected articulatedly at their adjacent ends by a common transverse joint and adapted individually to be mounted on and extended by a corresponding prop means into roof supporting engagement, and at least one leaf spring supported medially against displacement on said joint as a fulcrum with the corresponding free ends of said spring maintained in urging surface contact disposition upwardly against the correspondingly adjacent underside portions of said ends of said roof cap sections joined by said joint and arranged to take thereat the corresponding downward load exerted on said free ends by the corresponding roof cap sections upon downward and inward pivoting of said roof cap sections about said joint and to be displaced temporarily when under load out of its normal planar disposition substantially without physical deterioration.

2. Cap according to claim 1 wherein said spring is compound leaf spring in the form of a spring bundle having at least two leaf spring members therein.

3. Cap according to claim 1 wherein said joint is in the form of a common transverse pin.

4. Cap according to claim 3 wherein said pin carries a collar thereon having a spring seating portion and said spring is supported medially against displacement on said collar while the free spring ends are maintained in said urging surface contact disposition against said underside portions.

5. Cap according to claim 3 wherein said spring is bowed medially and extends in form fitting surface conwith said underside portions whereby to var the spring force against said underside portions and in turn vary the vertical disposition of the corresponding cap section with respect to said pin.

7. Multi-sectional roof cap for mine roof supporting prop means which comprises a pair of longitudinally extending individual roof cap sections interconnected articulatedly at their adjacent ends by a common transverse pin and adapted individually to be mounted on and extended by a corresponding prop means into roof supporting engagement, said pin carrying a collar thereon having a spring seating portion, and at least one leaf spring supported medially against displacement on said pin as a fulcrum by means of said collar with the corresponding free ends of said spring maintained in urging surface contact disposition upwardly against the correspondingly adjacent underside portions of said ends of said roof cap sections joined by said pin, said spring being provided with a medial threaded aperture and coacting medial adjustment screw inserted upwardly therethrough and seated in a corresponding threaded connection defined in the underside of said collar to connect vertically adjustably said spring to said collar whereby to vary the spring force against said underside portions and in turn vary the vertical disposition of the corresponding cap section with respect to said pin.

References Cited FOREIGN PATENTS 2/ 1962 Great Britain. 5/1964 Great Britain.

JACOB SHAPIRO, Primary Examiner 

